I need to calculate the local displacement vector for my deformed material and use that to calculate some other variables. I need to know when we say local, should I use the Spatial or the Material coordinate and also I need the syntax to write it mathematically and later calculate the divergence of that.
Are you doing geometrically linear or non-linear analysis? If linear, then Material and Spatial reference are the same. The above answer would then be fine (3D at least) for getting each displacement component.
With the displacement field uvec=[u, v, w], the divergence of this vector field could then be found using the syntax: d(u,x)+d(v,y)+d(w,z)
Thank you Rene, it is non-linear. Should it be d(u,X) or d(u,x) ?Also the "dot" notation works? like u.x instead of d?
Hi Richard
The material coordinates correspond to the undeformed geometry (Lagrangian), whereas the spatial coordinates (capital letters in COMSOL), whereas the spatial coordinates correspond to the deformed geometry (Eulerian), i.e. they move with the solid structure as it deformes or displaces. So the question really comes down to which divergence are you looking for, and then define it accordingly in COMSOL. Dot notation should work too, yes. But try all of this out with a simple case, for which you have an analytical solution, and see if it makes sense.
Let us know how it works out.
René
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